diff options
Diffstat (limited to 'epan/dissectors/packet-skype.c')
| -rw-r--r-- | epan/dissectors/packet-skype.c | 455 |
1 files changed, 455 insertions, 0 deletions
diff --git a/epan/dissectors/packet-skype.c b/epan/dissectors/packet-skype.c new file mode 100644 index 00000000..7acd4f4a --- /dev/null +++ b/epan/dissectors/packet-skype.c @@ -0,0 +1,455 @@ +/* packet-skype.c + * Routines for the disassembly of Skype + * + * Copyright 2009 Joerg Mayer (see AUTHORS file) + * + * Wireshark - Network traffic analyzer + * By Gerald Combs <gerald@wireshark.org> + * Copyright 1998 Gerald Combs + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +/* + * Documentation that formed the basis of the packet decoding: + * https://github.com/matthiasbock/OpenSkype/wiki/Skype's-UDP-Format + * For additional information see: + * https://gitlab.com/wireshark/wireshark/-/wikis/Skype + * + * TODO: + * - Authentication + * - TCP + * - Conversation stuff (to obtain external IPs for decryption) + * - Decryption (with given keys) + * - Test CRC check (requires working decryption) + * - Heuristics to reliably detect Skype traffic - most likely impossible + * to implement in Wireshark (see + * https://gitlab.com/wireshark/wireshark/-/wikis/Skype) + * - Improve tests + */ + +#include "config.h" + +#include <epan/packet.h> +#include <epan/conversation.h> + +void proto_register_skype(void); +void proto_reg_handoff_skype(void); + +static dissector_handle_t skype_handle; + +/* Things we may want to remember for a whole conversation */ +typedef struct _skype_udp_conv_info_t { + guint32 global_src_ip; + guint32 global_dst_ip; +} skype_udp_conv_info_t; + +/* protocol handles */ +static int proto_skype = -1; + +/* ett handles */ +static int ett_skype = -1; + +#define SKYPE_SOM_UNK_MASK 0xF0 +#define SKYPE_SOM_TYPE_MASK 0x0F + +/* hf elements */ +/* Start of Message */ +static int hf_skype_som_id = -1; +static int hf_skype_som_unk = -1; +static int hf_skype_som_type = -1; +/* Message body */ +/* Unknown_0 */ +static int hf_skype_unknown_0_unk1 = -1; +/* Payload */ +static int hf_skype_payload_iv = -1; +static int hf_skype_payload_crc = -1; +static int hf_skype_payload_enc_data = -1; +/* Resend */ +static int hf_skype_ffr_num = -1; +static int hf_skype_ffr_unk1 = -1; +static int hf_skype_ffr_iv = -1; +static int hf_skype_ffr_crc = -1; +static int hf_skype_ffr_enc_data = -1; +/* Nat info */ +static int hf_skype_natinfo_srcip = -1; +static int hf_skype_natinfo_dstip = -1; +/* Nat request */ +static int hf_skype_natrequest_srcip = -1; +static int hf_skype_natrequest_dstip = -1; +/* Audio */ +static int hf_skype_audio_unk1 = -1; +/* Unknown_f */ +static int hf_skype_unknown_f_unk1 = -1; +/* Unknown packet type */ +static int hf_skype_unknown_packet = -1; + + +#define PROTO_SHORT_NAME "SKYPE" +#define PROTO_LONG_NAME "SKYPE" + +typedef enum { + SKYPE_TYPE_UNKNOWN_0 = 0, + SKYPE_TYPE_PAYLOAD = 2, + SKYPE_TYPE_FFR = 3, + SKYPE_TYPE_NAT_INFO = 5, + SKYPE_TYPE_NAT_REPEAT = 7, + SKYPE_TYPE_AUDIO = 0xd, + SKYPE_TYPE_UNKNOWN_F = 0xf +} skype_type_t; + + +static const value_string skype_type_vals[] = { + { SKYPE_TYPE_UNKNOWN_0, "Unknown_0" }, + { SKYPE_TYPE_PAYLOAD, "Payload" }, + { SKYPE_TYPE_FFR, "Fragment/Forward/Resend" }, + { SKYPE_TYPE_NAT_INFO , "NAT info" }, + { SKYPE_TYPE_NAT_REPEAT,"NAT repeat" }, + { SKYPE_TYPE_AUDIO, "Audio" }, + { SKYPE_TYPE_UNKNOWN_F, "Unknown_F" }, + + { 0, NULL } +}; + + +static int +dissect_skype_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) +{ + proto_item *ti; + proto_tree *skype_tree = NULL; + guint32 offset = 0; + guint32 packet_length; + guint8 packet_type; + + /* XXX: Just until we know how to decode skype over tcp */ + packet_type = 255; + + packet_length = tvb_captured_length(tvb); + + col_set_str(pinfo->cinfo, COL_PROTOCOL, PROTO_SHORT_NAME); + col_add_str(pinfo->cinfo, COL_INFO, val_to_str(packet_type, + skype_type_vals, "Type 0x%1x")); + + if (tree) { + /* Start of message dissection */ + ti = proto_tree_add_item(tree, proto_skype, tvb, offset, -1, + ENC_NA); + skype_tree = proto_item_add_subtree(ti, ett_skype); + + /* Body dissection */ + switch (packet_type) { + + default: + proto_tree_add_item(skype_tree, hf_skype_unknown_packet, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + } + } + return offset; +} + +static int +dissect_skype_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) +{ + proto_item *ti; + proto_tree *skype_tree = NULL; + guint32 offset = 0; + guint32 packet_length; + guint8 packet_type, packet_unk; + + conversation_t *conversation = NULL; + skype_udp_conv_info_t *skype_udp_info; + + /* look up the conversation */ + conversation = find_or_create_conversation(pinfo); + + /* if conversation found get the data pointer that you stored */ + skype_udp_info = (skype_udp_conv_info_t *)conversation_get_proto_data(conversation, proto_skype); + if (!skype_udp_info) { + /* new conversation create local data structure */ + skype_udp_info = wmem_new(wmem_file_scope(), skype_udp_conv_info_t); + skype_udp_info->global_src_ip = 0; + skype_udp_info->global_dst_ip = 0; + conversation_add_proto_data(conversation, proto_skype, + skype_udp_info); + } + /* at this point the conversation data is ready */ + + packet_type = tvb_get_guint8(tvb, 2) & SKYPE_SOM_TYPE_MASK; + packet_unk = (tvb_get_guint8(tvb, 2) & SKYPE_SOM_UNK_MASK) >> 4; + + packet_length = tvb_captured_length(tvb); + + col_set_str(pinfo->cinfo, COL_PROTOCOL, PROTO_SHORT_NAME); + col_add_str(pinfo->cinfo, COL_INFO, val_to_str(packet_type, + skype_type_vals, "Type 0x%1x")); + if (packet_unk) { + col_append_fstr(pinfo->cinfo, COL_INFO, " Unk: %1x", packet_unk); + } + + if (tree) { + /* Start of message dissection */ + ti = proto_tree_add_item(tree, proto_skype, tvb, offset, -1, + ENC_NA); + skype_tree = proto_item_add_subtree(ti, ett_skype); + + proto_tree_add_item(skype_tree, hf_skype_som_id, tvb, offset, 2, + ENC_BIG_ENDIAN); + offset += 2; + proto_tree_add_item(skype_tree, hf_skype_som_unk, tvb, offset, 1, + ENC_BIG_ENDIAN); + proto_tree_add_item(skype_tree, hf_skype_som_type, tvb, offset, 1, + ENC_BIG_ENDIAN); + offset += 1; + + /* Body dissection */ + switch (packet_type) { + + case SKYPE_TYPE_UNKNOWN_0: + proto_tree_add_item(skype_tree, hf_skype_unknown_0_unk1, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + case SKYPE_TYPE_PAYLOAD: + proto_tree_add_item(skype_tree, hf_skype_payload_iv, tvb, offset, 4, + ENC_BIG_ENDIAN); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_payload_crc, tvb, offset, 4, + ENC_BIG_ENDIAN); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_payload_enc_data, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + case SKYPE_TYPE_FFR: + proto_tree_add_item(skype_tree, hf_skype_ffr_num, tvb, offset, 1, + ENC_BIG_ENDIAN); + offset += 1; + proto_tree_add_item(skype_tree, hf_skype_ffr_unk1, tvb, offset, 4, + ENC_BIG_ENDIAN); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_ffr_iv, tvb, offset, 4, + ENC_BIG_ENDIAN); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_ffr_crc, tvb, offset, 4, + ENC_BIG_ENDIAN); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_ffr_enc_data, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + case SKYPE_TYPE_NAT_INFO: + proto_tree_add_item(skype_tree, hf_skype_natinfo_srcip, tvb, offset, 4, + ENC_BIG_ENDIAN); + skype_udp_info->global_src_ip = tvb_get_ipv4(tvb, offset); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_natinfo_dstip, tvb, offset, 4, + ENC_BIG_ENDIAN); + skype_udp_info->global_dst_ip = tvb_get_ipv4(tvb, offset); + offset += 4; + break; + case SKYPE_TYPE_NAT_REPEAT: + proto_tree_add_item(skype_tree, hf_skype_natrequest_srcip, tvb, offset, 4, + ENC_BIG_ENDIAN); + skype_udp_info->global_src_ip = tvb_get_ipv4(tvb, offset); + offset += 4; + proto_tree_add_item(skype_tree, hf_skype_natrequest_dstip, tvb, offset, 4, + ENC_BIG_ENDIAN); + skype_udp_info->global_dst_ip = tvb_get_ipv4(tvb, offset); + offset += 4; + break; + case SKYPE_TYPE_AUDIO: + proto_tree_add_item(skype_tree, hf_skype_audio_unk1, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + case SKYPE_TYPE_UNKNOWN_F: + proto_tree_add_item(skype_tree, hf_skype_unknown_f_unk1, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + default: + proto_tree_add_item(skype_tree, hf_skype_unknown_packet, tvb, offset, -1, + ENC_NA); + offset = packet_length; + break; + } + } + return offset; +} + +static gboolean +test_skype_udp(tvbuff_t *tvb) +{ + /* Minimum of 3 bytes, check for valid message type */ + if (tvb_captured_length(tvb) > 3) + { + guint8 type = tvb_get_guint8(tvb, 2) & 0xF; + if ( type == 0 || + /* FIXME: Extend this by minimum or exact length per message type */ + type == 2 || + type == 3 || + type == 5 || + type == 7 || + type == 0xd || + type == 0xf + ) + { + return TRUE; + } + } + return FALSE; +} + +static gboolean +dissect_skype_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) +{ + if ( !test_skype_udp(tvb) ) { + return FALSE; + } + + dissect_skype_udp(tvb, pinfo, tree); + return TRUE; +} + +static int +dissect_skype_static(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) +{ + /* + * Don't test for valid packet - we only end here when + * the user did a decode-as. + */ + if (pinfo->ptype == PT_UDP) { + return dissect_skype_udp(tvb, pinfo, tree); + } else if (pinfo->ptype == PT_TCP) { + return dissect_skype_tcp(tvb, pinfo, tree); + } + return 0; +} + +void +proto_register_skype(void) +{ + static hf_register_info hf[] = { + + /* Start of message fields */ + { &hf_skype_som_id, + { "ID", "skype.som.id", FT_UINT16, BASE_HEX, NULL, + 0x0, "Message ID", HFILL }}, + + { &hf_skype_som_unk, + { "Unknown", "skype.som.unk", FT_UINT8, BASE_HEX, NULL, + SKYPE_SOM_UNK_MASK, NULL, HFILL }}, + + { &hf_skype_som_type, + { "Type", "skype.som.type", FT_UINT8, BASE_HEX, VALS(skype_type_vals), + SKYPE_SOM_TYPE_MASK, "Message type", HFILL }}, + + /* Message body */ + + /* Unknown_0 */ + { &hf_skype_unknown_0_unk1, + { "Unknown1", "skype.unknown_0.unk1", FT_BYTES, BASE_NONE, NULL, + 0x0, NULL, HFILL }}, + + /* Payload */ + { &hf_skype_payload_iv, + { "IV", "skype.payload.iv", FT_UINT32, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + { &hf_skype_payload_crc, + { "CRC", "skype.payload.crc", FT_UINT32, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + { &hf_skype_payload_enc_data, + { "Enc Data", "skype.payload.encdata", FT_BYTES, BASE_NONE, NULL, + 0x0, NULL, HFILL }}, + + /* Resend */ + { &hf_skype_ffr_num, + { "Num", "skype.ffr.num", FT_UINT8, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + { &hf_skype_ffr_unk1, + { "Unk1", "skype.ffr.unk1", FT_UINT32, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + { &hf_skype_ffr_iv, + { "IV", "skype.ffr.iv", FT_UINT32, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + { &hf_skype_ffr_crc, + { "CRC", "skype.ffr.crc", FT_UINT32, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + { &hf_skype_ffr_enc_data, + { "Enc Data", "skype.ffr.encdata", FT_BYTES, BASE_NONE, NULL, + 0x0, NULL, HFILL }}, + + /* Nat info */ + { &hf_skype_natinfo_srcip, + { "Src IP", "skype.natinfo.srcip", FT_IPv4, BASE_NONE, NULL, + 0x0, "Global source IP", HFILL }}, + + { &hf_skype_natinfo_dstip, + { "Dst IP", "skype.natinfo.dstip", FT_UINT32, BASE_HEX, NULL, + 0x0, "Global destination IP", HFILL }}, + + /* Nat request */ + { &hf_skype_natrequest_srcip, + { "Src IP", "skype.natrequest.srcip", FT_IPv4, BASE_NONE, NULL, + 0x0, "Global source IP", HFILL }}, + + { &hf_skype_natrequest_dstip, + { "Dst IP", "skype.natrequest.dstip", FT_UINT32, BASE_HEX, NULL, + 0x0, NULL, HFILL }}, + + /* Audio */ + { &hf_skype_audio_unk1, + { "Unknown1", "skype.audio.unk1", FT_BYTES, BASE_NONE, NULL, + 0x0, NULL, HFILL }}, + + /* Unknown_F */ + { &hf_skype_unknown_f_unk1, + { "Unknown1", "skype.unknown_f.unk1", FT_BYTES, BASE_NONE, NULL, + 0x0, NULL, HFILL }}, + + /* Unknown packet */ + { &hf_skype_unknown_packet, + { "Unknown Packet", "skype.unknown_packet", FT_BYTES, BASE_NONE, NULL, + 0x0, NULL, HFILL }}, + + }; + static gint *ett[] = { + &ett_skype, + }; + + proto_skype = proto_register_protocol(PROTO_LONG_NAME, PROTO_SHORT_NAME, "skype"); + proto_register_field_array(proto_skype, hf, array_length(hf)); + proto_register_subtree_array(ett, array_length(ett)); + + skype_handle = register_dissector("skype", dissect_skype_static, proto_skype); +} + +void +proto_reg_handoff_skype(void) +{ + dissector_add_for_decode_as_with_preference("tcp.port", skype_handle); + dissector_add_for_decode_as_with_preference("udp.port", skype_handle); + + heur_dissector_add("udp", dissect_skype_heur, "Skype over UDP", "skype_udp", proto_skype, HEURISTIC_DISABLE); +} + +/* + * Editor modelines - https://www.wireshark.org/tools/modelines.html + * + * Local variables: + * c-basic-offset: 8 + * tab-width: 8 + * indent-tabs-mode: t + * End: + * + * vi: set shiftwidth=8 tabstop=8 noexpandtab: + * :indentSize=8:tabSize=8:noTabs=false: + */ |